update bootloader version for atmel-samd

Author: dhalbert

_data/bootloaders.json

@@ -4,7 +4,7 @@
             "version": "0.9.2"
         },
         "atmel-samd": {
-            "version": "v3.15.0"
+            "version": "v3.16.0"
         },
         "esp32s2": {
             "version": "0.20.1"